Systems and methods providing location feedback for additive manufacturing

ABSTRACT

A system and method to correct for deposition errors during a robotic welding additive manufacturing process. The system includes a welding power source to sample instantaneous parameter pairs of welding output current and wire feed speed in real time during a robotic welding additive manufacturing process while creating a current weld layer of a 3D workpiece part. An instantaneous ratio of welding output current and wire feed speed are determined for each instantaneous parameter pair. A short term running average ratio is determined based on the instantaneous ratios. A relative correction factor is generated based on at least the short term running average ratio and is used in real time while creating the current weld layer to compensate for deviations in a deposit level from a desired deposit level for the current weld layer.

This U.S. patent application is a continuation-in-part (CIP) of U.S.patent application Ser. No. 15/465,021, filed on Mar. 21, 2017, which isa continuation-in-part (CIP) of U.S. patent application Ser. No.14/134,188, filed on Dec. 19, 2013 (now U.S. Pat. No. 9,815,135 issuedon Nov. 14, 2017), which claims the benefit of and priority to U.S.provisional patent application Ser. No. 61/894,035 filed on Oct. 22,2013, all of which are incorporated herein by reference in theirentirety.

TECHNICAL FIELD

Certain embodiments of the present invention relate to arc welding. Moreparticularly, certain embodiments of the present invention relate tosystems and methods providing location feedback for a robotic weldingadditive manufacturing process.

BACKGROUND

During a robotic welding additive manufacturing process, successivelayers of metal material are build up to create a workpiece part. Arobotic welding unit is used to build-up the workpiece part,layer-by-layer, over time as commanded by a robot controller of therobotic welding unit. The robot controller may include software thatreads a 3D model of the workpiece part to be created using an additive(layer-by-layer) manufacturing process. The robot controllerprogrammatically splits the 3D model into a plurality of layers andplans a welding path for each of the individual layers to perform thebuild-up of the part. An expected weld deposition is determined for eachlayer, resulting in an expected height for each deposited layer.However, as actual layer-by-layer welding proceeds, the actual resultantheight for any given layer may deviate from the expected or desiredheight, due to factors such as, for example, surface conditions of theworkpiece part substrate (e.g., temperature or position on substrate)and the accuracy with which certain welding parameters can becontrolled.

Further limitations and disadvantages of conventional, traditional, andproposed approaches will become apparent to one of skill in the art,through comparison of such systems and methods with embodiments of thepresent invention as set forth in the remainder of the presentapplication with reference to the drawings.

SUMMARY

A system and method to correct for height error during a robotic weldingadditive manufacturing process are provided. One or both of a weldingoutput current and a wire feed speed are sampled during a roboticwelding additive manufacturing process when creating a current weldlayer. A plurality of instantaneous contact tip-to-work distances(CTWD's) are determined based on at least one or both of the weldingoutput current and the wire feed speed. An average CTWD is determinedbased on the plurality of instantaneous CTWD's. A correction factor isgenerated, based on at least the average CTWD, which is used tocompensate for any error in height of the current weld layer and/or thenext weld layer.

In one embodiment, a welding system is provided having a welding powersource. The welding power source is configured to sample, in real time,instantaneous parameter pairs during a robotic welding additivemanufacturing process while creating a current weld layer of a 3Dworkpiece part. Each instantaneous parameter pair of the instantaneousparameter pairs includes a welding output current and a wire feed speed.The welding power source is also configured to determine aninstantaneous contact tip-to-work distance in real time for, and basedon at least, each parameter pair of the instantaneous parameter pairs aseach parameter pair is sampled during creation of the current weldlayer. The welding power source is further configured to determine, inreal time, a running average contact tip-to-work distance based on eachinstantaneous contact tip-to-work distance as each instantaneous contacttip-to-work distance is determined during creation of the current weldlayer. The welding power source is also configured to generate acorrection factor. The correction factor is based on at least therunning average contact tip-to-work distance and is to be used in realtime, while creating the current weld layer of the 3D workpiece part, tocompensate for deviations in a deposit level from a desired depositlevel for the current weld layer. In one embodiment, the instantaneouscontact tip-to-work distance may further be based on one or more of awelding output voltage, a welding electrode type, a welding electrodediameter, or a shielding gas used. The running average contacttip-to-work distance may be one of a simple running mathematical averageor a weighted average of the instantaneous contact tip-to-workdistances. In one embodiment, the welding power source is configured togenerate the correction factor at least in part by comparing the runningaverage contact tip-to-work distance to a setpoint contact tip-to-workdistance. The welding power source may also be configured to adjust, inreal time, one or more of a travel speed, a weld duration, or a wirefeed speed of the welding system during creation of the current weldlayer in response to the correction factor. Adjusting the travel speedin response to the correction factor may include taking into account apreset travel speed. Adjusting the weld duration in response to thecorrection factor may include taking into account a preset weldduration. Adjusting the wire feed speed in response to the correctionfactor may include taking into account a preset wire feed speed. In oneembodiment, the correction factor is further based on one or more 3Dmodel parameters corresponding to the 3D workpiece part or robotparameters provided by a robot controller for a current weld operationfor the current weld layer. The 3D model parameters and robot parametersmay include one or more of a designated height of the current weld layeror a designated position of a welding tool for the current weld layer.In one embodiment, the welding system includes a robot having a robotcontroller configured to operatively communicate with the welding powersource. In one embodiment, the welding system includes a welding tooloperatively connected to the robot. In one embodiment, the weldingsystem includes a wire feeder operatively connected to the welding tooland the welding power source.

In one embodiment, a welding system is provided having a welding powersource. The welding power source is configured to sample, in real time,instantaneous parameter pairs during a robotic welding additivemanufacturing process while creating a current weld layer of a 3Dworkpiece part. Each instantaneous parameter pair of the instantaneousparameter pairs includes a welding output current and a wire feed speed.The welding power source is also configured to determine aninstantaneous contact tip-to-work distance in real time for, and basedon at least, each parameter pair of the instantaneous parameter pairs aseach parameter pair is sampled during creation of the current weldlayer. The welding power source is further configured to determine, inreal time, a running average contact tip-to-work distance based on eachinstantaneous contact tip-to-work distance as each instantaneous contacttip-to-work distance is determined during creation of the current weldlayer. The welding power source is also configured to determine a totalaverage contact tip-to-work distance based on each instantaneous contacttip-to-work distance determined over the entire current weld layer. Thewelding power source is further configured to adjust, in real time, oneor more of a weld duration, a travel speed, or a wire feed speed of thewelding system during creation of the current weld layer in response tothe running average contact tip-to-work distance. The welding powersource is also configured to generate a correction factor to be usedwhen creating a next weld layer of the 3D workpiece part based on atleast the total average contact tip-to-work distance. In accordance withone embodiment, the welding power source includes a controllerconfigured to determine the instantaneous contact tip-to-work distance,determine the running average contact tip-to-work distance, determinethe total average contact tip-to-work distance, adjust one or more ofthe weld duration, the travel speed, or the wire feed speed during thecreation of the current weld layer, and generate the correction factorto be used when creating the next weld layer. In one embodiment, theinstantaneous contact tip-to-work distance is further based on one ormore of a welding output voltage, a welding electrode type, a weldingelectrode diameter, or a shielding gas used. In one embodiment,adjusting the travel speed in response to the running average contacttip-to-work distance includes taking into account a preset travel speed.Adjusting the weld duration in response to the running average contacttip-to-work distance includes taking into account a preset weldduration. Adjusting the wire feed speed in response to the runningaverage contact tip-to-work distance includes taking into account apreset wire feed speed. In one embodiment, the correction factor isfurther based on one or more of 3D model parameters corresponding to the3D workpiece part or robot parameters provided by a robot controller fora next weld operation for the next weld layer. The 3D model parametersand the robot parameters may include one or more of a designated heightof the next weld layer or a designated position of a welding tool forthe next weld layer. The total average contact tip-to-work distance isone of a simple mathematical average of the instantaneous contacttip-to-work distances determined over the entire current weld layer, aweighted average of the instantaneous contact tip-to-work distancesdetermined over the entire current weld layer, or a running average ofthe instantaneous contact tip-to-work distances determined over theentire current weld layer. In one embodiment, the welding systemincludes a robot having a robot controller configured to operativelycommunicate with the welding power source, a welding tool operativelyconnected to the robot, and a wire feeder operatively connected to thewelding tool and the welding power source.

Details of illustrated embodiments of the present invention will be morefully understood from the following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a diagram of an exemplary embodiment of a roboticwelding cell unit;

FIG. 2 illustrates a schematic block diagram of an exemplary embodimentof the welding power source of the robotic welding cell unit of FIG. 1operatively connected to a consumable welding electrode and a workpiecepart;

FIG. 3 illustrates a diagram of an exemplary embodiment of a portion ofthe welding gun of the robotic welding cell unit of FIG. 1 providing awelding wire electrode that interacts with a workpiece part during anadditive manufacturing arc welding process;

FIGS. 4A and 4B illustrate the concept of contact tip-to-work distance(CTWD) with and without the presence of an arc;

FIG. 5 illustrates an exemplary embodiment of a two-dimensional graphhaving two plots showing the relationship between CTWD and weldingoutput current (amperage) for two different welding wires, being of thesame type but of two different sizes, for an arc welding process at agiven wire feed speed when a particular type of welding gas is used;

FIG. 6 illustrates an exemplary embodiment of a three-dimensional graphshowing the relationship between CTWD, welding output current(amperage), and wire feed speed, being of a particular type and size,for an arc welding process when a particular type of welding gas isprovided;

FIG. 7 illustrates an exemplary embodiment of a portion of thecontroller of the welding power source of FIG. 2 configured to determinean actual, instantaneous CTWD;

FIG. 8 illustrates an exemplary embodiment of a portion of thecontroller of the welding power source of FIG. 2 configured to determinean average CTWD over time, from the instantaneous CTWD's, and compute acorrection factor;

FIG. 9 illustrates a flow chart of an embodiment of a method forcorrecting for additive manufacturing height error on a layer-by-layerbasis during a robotic welding additive manufacturing process (RWAMP);

FIG. 10 illustrates an example of a robotic welding additivemanufacturing process employing the method of FIG. 9;

FIG. 11 illustrates an exemplary embodiment of a portion of thecontroller of the welding power source of FIG. 2 to compensate fordeviations in a deposit level from a desired deposit level for a currentweld layer; and

FIG. 12 illustrates another exemplary embodiment of a portion of thecontroller of the welding power source of FIG. 2 to compensate fordeviations in a deposit level from a desired deposit level for a currentweld layer.

DETAILED DESCRIPTION

The following are definitions of exemplary terms that may be used withinthe disclosure. Both singular and plural forms of all terms fall withineach meaning:

“Software” or “computer program” as used herein includes, but is notlimited to, one or more computer readable and/or executable instructionsthat cause a computer or other electronic device to perform functions,actions, and/or behave in a desired manner. The instructions may beembodied in various forms such as routines, algorithms, modules orprograms including separate applications or code from dynamically linkedlibraries. Software may also be implemented in various forms such as astand-alone program, a function call, a servlet, an applet, anapplication, instructions stored in a memory, part of an operatingsystem or other type of executable instructions. It will be appreciatedby one of ordinary skill in the art that the form of software isdependent on, for example, requirements of a desired application, theenvironment it runs on, and/or the desires of a designer/programmer orthe like.

“Computer” or “processing element” or “computer device” as used hereinincludes, but is not limited to, any programmed or programmableelectronic device that can store, retrieve, and process data.“Non-transitory computer-readable media” include, but are not limitedto, a CD-ROM, a removable flash memory card, a hard disk drive, amagnetic tape, and a floppy disk.

“Welding tool”, as used herein, refers to, but is not limited to, awelding gun, a welding torch, or any welding device that accepts aconsumable welding wire for the purpose of applying electrical power tothe consumable welding wire provided by a welding power source.

“Welding output circuit path”, as used herein, refers to the electricalpath from a first side of the welding output of a welding power source,through a first welding cable (or a first side of a welding cable), to awelding electrode, to a workpiece (either through a short or an arcbetween the welding electrode and the workpiece), through a secondwelding cable (or a second side of a welding cable), and back to asecond side of the welding output of the welding power source.

“Welding cable”, as used herein, refers to the electrical cable that maybe connected between a welding power source and a welding electrode andworkpiece (e.g. through a welding wire feeder) to provide electricalpower to create an arc between the welding electrode and the workpiece.

“Welding output”, as used herein, may refer to the electrical outputcircuitry or output port or terminals of a welding power source, or tothe electrical power, voltage, or current provided by the electricaloutput circuitry or output port of a welding power source.

“Computer memory”, as used herein, refers to a storage device configuredto store digital data or information which can be retrieved by acomputer or processing element.

“Controller”, as used herein, refers to the logic circuitry and/orprocessing elements and associated software or program involved incontrolling a welding power source or a welding robot.

The terms “signal”, “data”, and “information” may be usedinterchangeably herein and may be in digital or analog form.

The term “welding parameter” is used broadly herein and may refer tocharacteristics of a portion of a welding output current waveform (e.g.,amplitude, pulse width or duration, slope, electrode polarity), awelding process (e.g., a short arc welding process or a pulse weldingprocess), wire feed speed, a modulation frequency, or a welding travelspeed.

With reference to FIG. 1, a robotic welding cell unit 10 generallyincludes a frame 12, a robot 14 disposed within the frame, and a weldingtable 16 also disposed within the frame. The robotic welding cell unit10 is useful for building up a workpiece part 22 on a substrate throughan additive manufacturing process, as described in more detail belowherein.

In the depicted embodiment, the frame 12 includes a plurality of sidewalls and doors to enclose the robot 14 and the welding table 16. Eventhough a substantially rectangular configuration is shown in a planview, the frame 12, and the unit 10, can take numerous configurations.

A front access door 26 mounts to the frame 12 to provide access to theinterior of the frame. Similarly, a rear access door 28 also mounts tothe frame 12. Windows 32 can be provided on either door (only depictedon front door 26). The windows can include a tinted safety screen, whichis known in the art.

A control panel 40 is provided on the frame 12 adjacent the front door26. Control knobs and/or switches provided on the control panel 40communicate with controls housed in a controls enclosure 42 that is alsomounted to the frame 12. The controls on the control panel 40 can beused to control operations performed in the unit 10 in a similar mannerto controls used with known welding cell units.

In accordance with an embodiment, the robot 14 is mounted on a pedestalthat mounts on a support (not shown). The robot 14 used in the depictedembodiment can be an ARC Mate® 100/Be robot available from FANUCRobotics America, Inc. Other similar robots can also be used. The robot14 in the depicted embodiment is positioned with respect to the weldingtable 16 and includes eleven axes of movement. If desired, the pedestal(not shown) can rotate with respect to the support (not shown) similarto a turret. Accordingly, some sort of drive mechanism, e.g. a motor andtransmission (not shown), can be housed in the pedestal and/or thesupport for rotating the robot 14.

A welding gun 60 attaches to a distal end of the robot arm 14. Thewelding gun 60 can be similar to those that are known in the art. Aflexible tube or conduit 62 attaches to the welding gun 60. Consumablewelding electrode wire 64, which can be stored in a container 66, isdelivered to the welding gun 60 through the conduit 62. A wire feeder68, which can be a PF 10 R-II wire feeder available from The LincolnElectric Company for example, attaches to the frame 12 to facilitate thedelivery of welding wire 64 to the welding gun 60.

Even though the robot 14 is shown mounted to a base or lower portion ofthe frame 12, if desired, the robot 14 can mount in a similar manner asthe robot disclosed in U.S. Pat. No. 6,772,932. That is, the robot canmount to an upper structure of the frame and extend downwardly into thecell unit 10.

With reference back to the embodiment depicted in FIG. 1, a weldingpower source 72 for the welding operation mounts to and rests on aplatform 74 that is connected to and can be a part of the frame 12. Thewelding power source 72 in the depicted embodiment is a PW 455 M (nonSTT) available from The Lincoln Electric Company; however, othersuitable power sources can be used for the welding operation. A robotcontroller 76, which controls the robot 14, also rests and mounts on theplatform 74. The robot controller typically accompanies the robot 14.

The robotic welding cell unit 10 may also include a shielding gas supply(not shown). During operation, the wire feeder 68, the welding gun 60,the shielding gas supply, and the welding power source 72 areoperatively connected to allow an electric arc to be created between awelding wire and a workpiece part 22 to create a weld layer as is wellknown in the art. In accordance with an embodiment, shielding gases maybe used during a gas metal arc welding (GMAW) process to protect thewelding region from atmospheric gases such as oxygen or nitrogen, forexample. Such atmospheric gases may cause various weld metal defectssuch as, for example, fusion defects, embrittlement, and porosity.

The type of shielding gas, or combination of shielding gases used dependon the material being welded and the welding process. The rate of flowof the shielding gas to be provided depends on the type of shieldinggas, the travel speed, the welding current, the weld geometry, and themetal transfer mode of the welding process. Inert shielding gasesinclude argon and helium. However, there may be situations when it isdesirable to use other shielding gases or combinations of gases such as,for example, carbon dioxide (CO2) and oxygen. In accordance with anembodiment, a shielding gas may be fed to a welding tool during an arcwelding process such that the welding tool disperses the shielding gasto the weld region during the welding process.

Selection of a welding wire or electrode is dependent on the compositionof the workpiece part being additively welded, the welding process, theconfiguration of the weld layer, and the surface conditions of theworkpiece part substrate. Welding wire selection may largely affect themechanical properties of the resultant weld layers and may be a maindeterminant of weld layer quality. It may be desirable for the resultantweld metal layers to have mechanical properties like those of the basesubstrate material, without defects such as discontinuities,contaminants, or porosity.

Existing welding wire electrodes often contain deoxidizing metals suchas silicon, manganese, titanium, and aluminum in relatively smallpercentages to help prevent oxygen porosity. Some electrodes may containmetals such as titanium and zirconium to avoid nitrogen porosity.Depending on the welding process and base substrate material beingwelded upon, the diameters of the electrodes used in gas metal arcwelding (GMAW) typically range from 0.028-0.095 inches, but may be aslarge as 0.16 inches. The smallest electrodes, generally up to 0.045inches in diameter, may be associated with a short-circuit metaltransfer process, while electrodes used for spray-transfer processes maybe at least 0.035 inches in diameter.

FIG. 2 illustrates a schematic block diagram of an exemplary embodimentof the welding power source 72 of the robotic welding cell unit 10 ofFIG. 1 operatively connected to a consumable welding electrode 64 and aworkpiece part 22. The welding power source 72 includes a switchingpower supply 105 having a power conversion circuit 110 and a bridgeswitching circuit 180 providing welding output power between the weldingelectrode 64 and the workpiece part 22. The power conversion circuit 110may be transformer based with a half bridge output topology. Forexample, the power conversion circuit 110 may be of an inverter typethat includes an input power side and an output power side, for example,as delineated by the primary and secondary sides, respectively, of awelding transformer. Other types of power conversion circuits arepossible as well such as, for example, a chopper type having a DC outputtopology. The power source 100 also includes a bridge switching circuit180 that is operatively connected to the power conversion circuit 110and is configured to switch a direction of the polarity of the weldingoutput current (e.g., for AC welding).

The power source 72 further includes a waveform generator 120 and acontroller 130. The waveform generator 120 generates welding waveformsat the command of the controller 130. A waveform generated by thewaveform generator 120 modulates the output of the power conversioncircuit 110 to produce the welding output current between the electrode64 and the workpiece part 22. The controller 130 also commands theswitching of the bridge switching circuit 180 and may provide controlcommands to the power conversion circuit 110.

The welding power source 72 further includes a voltage feedback circuit140 and a current feedback circuit 150 to monitor the welding outputvoltage and current between the electrode 64 and the workpiece part 22and provide the monitored voltage and current back to the controller130. The feedback voltage and current may be used by the controller 130to make decisions with respect to modifying the welding waveformgenerated by the waveform generator 120 and/or to make other decisionsthat affect operation of the power source 72, for example. In accordancewith an embodiment, the controller 130 is used to determine CTWD duringa welding process, and use the CTWD to adjust a weld time duration (WTD)and/or a wire feed speed (WFS), as is discussed in more detail laterherein.

In accordance with an embodiment, the switching power supply 105, thewaveform generator 120, the controller 130, the voltage feedback circuit140, and the current feedback circuit 150 constitute the welding powersource 72. The robotic welding cell unit 10 also includes a wire feeder68 that feeds the consumable wire welding electrode 64 toward theworkpiece part 22 through the welding gun (welding tool) 60 at aselected wire feed speed (WFS). The wire feeder 68, the consumablewelding electrode 64, and the workpiece part 22 are not part of thewelding power source 72 but may be operatively connected to the weldingpower source 72 via one or more welding output cables.

FIG. 3 illustrates a diagram of an exemplary embodiment of a portion ofthe welding gun 60 of the robotic welding cell unit 10 of FIG. 1providing a welding wire electrode 64 that interacts with a workpiecepart 22 during an additive manufacturing arc welding process. Thewelding gun 60 may have an insulated conductor tube 61, an electrodeconduit 63, a gas diffuser 65, a contact tip 67, and a wire electrode 64feeding through the gun 60. A control switch, or trigger, (not shown)when activated by the robot 14, starts the wire feed, electric power,and the shielding gas flow, causing an electric arc to be establishedbetween the electrode 64 and the workpiece part 22. The contact tip 67is electrically conductive and is connected to the welding power source72 through a welding cable and transmits electrical energy to theelectrode 64 while directing the electrode 64 toward the workpiece part22. The contact tip 67 is secured and sized to allow the electrode 64 topass while maintaining electrical contact.

The wire feeder 68 supplies the electrode 64 to the workpiece part 22,driving the electrode 64 through the conduit 62 and on to the contacttip 67. The wire electrode 64 may be fed at a constant feed rate, or thefeed rate may be varied based on the arc length and the welding voltage.Some wire feeders can reach feed rates as high as 1200 in/min), however,feed rates for semiautomatic GMAW typically range from 75-400 in/min.

On the way to the contact tip 67, the wire electrode 64 is protected andguided by the electrode conduit 63, which helps prevent kinking andmaintains an uninterrupted feeding of the wire electrode 64. The gasdiffuser 65 directs the shielding gas evenly into the welding zone. Agas hose from the tank(s) of shielding gas supplies the gas to the gasdiffuser 65.

FIGS. 4A and 48 illustrate the concept of contact tip-to-work distance(CTWD) with and without the presence of an arc. In FIG. 4A, the CTWD isshown as the distance between the end of the contact tip 67 and a toplayer of the workpiece part 22 with no arc established between theelectrode 64 and the workpiece part 22. In FIG. 48, the CTWD is shown asthe distance between the end of the contact tip 67 and the top layer ofthe workpiece part 22 with an arc established between the electrode 64and the workpiece part 22. Again, keeping a consistent, desired contacttip-to-work distance (CTWD) during a welding process is important. Ingeneral, as CTWD increases, the welding current decreases. A CTWD thatis too long may cause the welding electrode to get too hot and may alsowaste shielding gas. Furthermore, the desired CTWD may be different fordifferent welding processes.

In accordance with an embodiment, the workpiece part 22 is built up,layer-by-layer, over time as commanded by the robot controller 76. Therobot controller 76 includes software that reads a 3D model of theworkpiece part 22 to be created using an additive (layer-by-layer)manufacturing process. The robot controller 76 programmatically splitsthe 3D model into a plurality of layers and plans a welding path foreach of the individual layers to perform the build-up of the part 22. Anexpected weld deposition is determined for each layer, resulting in anexpected height for each deposited layer. However, as actuallayer-by-layer welding proceeds, the actual resultant height for anygiven layer may deviate from the expected or desired height, due tofactors such as, for example, surface conditions of the workpiece partsubstrate and the accuracy with which certain welding parameters can becontrolled. Therefore, in accordance with an embodiment, CTWD ismonitored for each layer during the welding process and used tocompensate for errors in the height dimension as described below hereinin detail.

FIG. 5 illustrates an exemplary embodiment of a two-dimensional graph500 having two plots 510 and 520 showing the relationship between CTWDand welding output current (amperage) for two different welding wires,being of the same type and fed at the same fixed rate, but being of twodifferent diameters, for an arc welding process when a particular typeof welding gas is used. In accordance with an embodiment, the actualinstantaneous CTWD during a welding process may be determined in realtime by the controller 130 based on the welding output current(amperage), the welding electrode type, the welding electrode diameter,the wire feed speed (WFS), and the shielding gas used. As the CTWDchanges in real time during a welding process, the welding outputcurrent (amperage) will reflect that change in real time, as defined bythe appropriate plot (e.g., 510 or 520). As the actual CTWD changes inreal time during the welding process, the controller 130, receiving thewelding output current value fed back from the current feedback circuit150, and already knowing the selected wire electrode type/diameter,shielding gas mixture, and wire feed speed, determines the actual CTWD.

In accordance with an embodiment, plot 510 corresponds to a welding wireelectrode, having a diameter of 0.045 inches and being of a mild steel,copper coated type, used in a welding process providing a mixture of 90%argon shielding gas and 10% carbon dioxide shielding gas. Furthermore,in accordance with an embodiment, plot 520 corresponds to a welding wireelectrode, having a diameter of 0.052 inches and being of a same mildsteel, copper coated type, used in a welding process providing a samemixture of 90% argon shielding gas and 10% carbon dioxide shielding gas.As can be seen from FIG. 5, as the diameter of the welding wire of thesame type is changed to an increased diameter, the plot representing therelationship of CTWD vs. amperage moves outward from the origin of thegraph 500.

In accordance with various embodiments, the relationship between CTWDand amperage for a combination of welding electrode type, weldingelectrode diameter, wire feed speed, and shielding gas used may bedetermined experimentally or through analysis based on theory. Once sucha relationship is determined, the relationship may be expressed orstored in the controller 130 as a look-up-table (LUT) or as amathematical transfer function or algorithm, for example.

In accordance with an alternative embodiment, the wire feed speed (WFS)may vary during the welding process (e.g., based on the arc length andthe welding voltage) and, therefore, the LUT or mathematical transferfunction may reflect the effect of a changing wire feed speed on CTWD.For example, FIG. 6 illustrates an exemplary embodiment of athree-dimensional graph 600 showing the relationship between CTWD,welding output current (amperage), and wire feed speed (WFS) for awelding wire, being of a particular type and size, for an arc weldingprocess when a particular type of welding gas is provided. The plot 610on the graph 600 forms a surface. In accordance with an embodiment, theactual instantaneous CTWD during a welding process may be determined inreal time by the controller 130 based on the welding output current(amperage), the wire feed speed, the welding electrode type, the weldingelectrode diameter, and the shielding gas used.

As the actual CTWD changes in real time during a welding process, thepaired welding output current (amperage) and WFS (parameter pair) willreflect that change in real time, as defined by the surface plot 610 ofthe graph 600. Furthermore, as the actual CTWD changes in real timeduring the welding process, the controller 130, receiving the weldingoutput current (amperage) value fed back from the current feedbackcircuit 150 and the WFS value fed back from the wire feeder 68, andalready knowing the selected wire electrode type/diameter and shieldinggas mixture, determines the actual CTWD. FIG. 6 shows an example of anamperage/WFS parameter pair 611 corresponding to an actual CTWD value612 as determined by the surface plot 610 of the graph 600. For othercombinations of welding electrode type, welding electrode diameter, andshielding gas used, plots of other surfaces will define the relationshipof CTWD, WFS, and amperage. In accordance with an alternativeembodiment, taking into consideration the welding output voltage as fedback to the controller 130 from the voltage feedback circuit 140 mayprovide a more accurate determination of actual instantaneous CTWD.

In accordance with various embodiments, the relationship between CTWD,WFS, and amperage for a combination of welding electrode type, weldingelectrode diameter, and shielding gas used may be determinedexperimentally or through analysis based on theory. Once such arelationship is determined, the relationship may be expressed or storedin the controller 130 as a look-up-table (LUT) or as a mathematicaltransfer function expressed in software, for example.

FIG. 7 illustrates an exemplary embodiment of a portion 700 of thecontroller 130 of the welding power source 72 of FIG. 2 configured todetermine an actual, instantaneous CTWD. As shown in the embodiment ofFIG. 7, a LUT 710 is used to implement the relationship between theinputs 711 (WFS, wire type, wire size, amperage, voltage, and shieldinggas) and the output 712 (actual CTWD). The LUT 710 may be implemented infirmware, for example, as an EEPROM. In some embodiments, the inputs ofwelding output voltage or shielding gas may not be used. For anyparticular combination of inputs 711, an output 712 representing anactual and instantaneous CTWD, in real time, is produced.

FIG. 8 illustrates an exemplary embodiment of a portion 800 of thecontroller 130 of the welding power source 72 of FIG. 2 configured todetermine an average CTWD 812 over time, from the CTWD's 712 out of theLUT 710, and compute a correction factor. The correction factor can takethe form of a weld duration 822, a wire feed speed (WFS) 824, or both.FIG. 8 also shows the robot controller 76 communicatively interfacing tothe portion 800 of the controller 130 of the welding power source 72.Optionally or alternatively, the correction factor can take the form ofa travel speed of the welding gun.

In accordance with an embodiment, when a current weld operation is beingperformed to create a current weld layer at a current position on theworkpiece part 22, a plurality of instantaneous CTWD's 712 is determinedduring the current weld operation and an average CTWD 812 is computedfrom the plurality of instantaneous CTWD's 712 for the current weldlayer by an averaging module 810. A correction factor (e.g., weldduration 822, WFS 824, or both) for a next weld operation is computed bya correction factor module 820 based on the average CTWD 812 and furtherbased on 3D model/robot parameters corresponding to the next weldoperation which are received by the controller 130 from the robotcontroller 76. The correction factor is used by the welding power source72 to generate the next weld layer at the next workpiece part position(e.g., the next height position corresponding to the next weld layer)during the next weld operation.

In accordance with an embodiment, the average CTWD can be a simplemathematical average of the instantaneous CTWD's. In another embodiment,the average CTWD can be a weighted average. For example, more weight maybe given to the later instantaneous CTWD's (e.g., maybe the last four ofthe ten). In accordance with still another embodiment, the average CTWDcan be a running average, where the total number of samples ofinstantaneous CTWD's may vary from layer to layer. Other ways ofdetermining average CTWD that work well for different additivemanufacturing applications may be possible as well. Therefore, the term“average CTWD” is used in a broad sense herein.

In accordance with an embodiment, the 3D model/robot parameters mayinclude one or more of a designated height of the next weld layer and adesignated position of the welding gun 60. By knowing the 3D model/robotparameters for the next weld layer and the average CTWD from the currentweld layer, the weld duration and/or the WFS can be increased ordecreased for the next weld operation to generate the next weld layer.The averaging module 810 and the correction factor module 820 may beimplemented as software and/or hardware in the controller 130, inaccordance with various embodiments. For example, implementations assoftware running on a processor, or as firmware (e.g., a programmedEEPROM), are contemplated. Other implemented embodiments are possible aswell (e.g., a digital signal processor).

For example, when the average CTWD 812 for the current weld layer islonger than expected based on the 3D model/robot parameters, this may bean indication that the resultant current weld layer is too short inheight (e.g., not enough weld material was deposited to reach thedesignated height for this layer). Therefore, the weld duration and/orthe WFS for the next weld operation can be increased to deposit moreweld material for the next weld layer to compensate for the short heightof the current weld layer.

Similarly, when the average CTWD for the current weld layer is shorterthan expected, this may be an indication that the resultant current weldlayer is too high (e.g., too much weld material was deposited,overshooting the designated height for this layer). Therefore, the weldduration and/or the WFS for the next weld operation can be decreased todeposit less weld material for the next weld layer to compensate for thecurrent weld layer. In this manner, by allowing for a next weld layer tocompensate for a current weld layer, any error in a resultant overallheight of the workpiece part at a particular location, after all weldlayers are generated, may be minimized. In accordance with analternative embodiment, a travel speed of the welding gun may beadjusted (increased or decreased) for a next weld layer to helpcompensate for a current weld layer.

The relationship between weld duration (and/or wire feed speed), for anext weld layer, and average CTWD may be determined experimentally orthrough analysis based on theory, in accordance with variousembodiments. In general, determination of CTWD is more accurate in aregion that produces a larger amperage change for a given change in CTWD(e.g., see FIG. 5).

FIG. 9 illustrates a flow chart of an embodiment of a method 900 forcorrecting for additive manufacturing height error on a layer-by-layerbasis during a robotic welding additive manufacturing process (RWAMP).In step 910, sample one or both of welding output current and wire feedspeed during a robotic welding additive manufacturing process forcreating a current weld layer. In step 920, determine a plurality ofinstantaneous contact tip-to-work distances based on one or both of thewelding output current and the wire feed speed, as well as a weldingwire type, a welding wire size and, optionally, a welding gas type usedduring the robotic welding additive manufacturing process and/or awelding output voltage. In step 930, determine an average CTWD based onthe plurality of instantaneous CTWD's determined during the roboticwelding additive manufacturing process for the current weld layer. Instep 940, generate a correction factor to be used when generating a nextweld layer based on the average CTWD and one or more parameters from arobot controller used to control the robotic welding additivemanufacturing process.

FIG. 10 illustrates an example of a robotic welding additivemanufacturing process employing the method 900 of FIG. 9. In the processof FIG. 10, each layer of weld material is designated to be 50 mils inheight along the z-direction at a designated position on a workpiecesubstrate, where a mil is a thousandth of an inch. During the deposit ofeach layer at the designated position, approximately ten (10) samples ofinstantaneous CTWD are determined as described herein during the weldduration for each layer. Furthermore, the average CTWD is determinedfrom the ten (10) samples of instantaneous CTWD. In accordance with anembodiment, the correction factor for a layer may change or vary as thedesignated position across that layer changes.

In the example of FIG. 10, the average CTWD for layer N was determinedto be longer than expected and the height of layer N ended up being 40mils instead of the desired 50 mils. As a result, using the processdescribed herein, a correction factor was determined for the next layerN+1 based on at least the average CTWD for layer N, where the weldduration and the wire feed speed were each increased by determinedamounts to compensate for the height deficiency of layer N. As a result,the height of layer N+1 ended up being 60 mils, resulting in a totalheight of 100 mils from the bottom of layer N to the top of layer N+1,as desired. The process may proceed in a similar manner for all layersat the designated position, resulting in a minimized, acceptable errorin height at that designated position. Again, in accordance with anembodiment, in addition (or as an alternative) to weld duration and wirefeed speed, travel speed may be adjusted to compensate for the currentlayer. That is, any one or more of weld duration, wire feed speed, ortravel speed for a next layer may be adjusted to compensate for acurrent layer.

As an alternative, a correction factor can be generated in real time fora current welding layer. For example, a running average of instantaneousCTWD's may be computed during a welding process for a current layer. Asthe running average is monitored, adjustments may be made in the weldduration, the travel speed, the power source output, and/or the wirefeed speed in real time for the current weld layer, based on the runningaverage CTWD.

FIG. 11 illustrates an exemplary embodiment of a portion 1100 of thecontroller 130 of the welding power source 72 of FIG. 2 to compensatefor deviations in a deposit level (height) from a desired deposit level(desired height) for a current weld layer. As shown in FIG. 11, theportion 1100 of the controller 130 is configured to generate an adjustedtravel speed, an adjusted weld duration, an adjusted wire feed speed(WFS), and an adjusted power source output for the current layer. Inaccordance with one embodiment, the controller 130 of the welding powersource 72 communicates the adjusted travel speed to the robot controller76 such that the robot controller 76 can drive the robot 14 to move thewelding gun 60 at the adjusted travel speed. Similarly, the controller130 of the welding power source 72 communicates the adjusted WFS to thewire feeder 68 such that the wire feeder 68 can drive the weldingelectrode (wire) at the adjusted WFS.

Referring again to FIG. 11, as the running average (RA) CTWD is beinggenerated during deposition of a current welding layer, the runningaverage CTWD is compared to a CTWD setpoint by a comparator 1110. TheCTWD setpoint is a numerical value representing the desired CTWD. Theoutput of the comparator 1110 is a correction factor. The correctionfactor may be a difference of the running average CTWD and the CTWDsetpoint, in accordance with one embodiment. In accordance with anotherembodiment, the comparator 1110 may be replaced by a LUT (orfunction/algorithm executed by a processor) providing a relationshipbetween the output (correction factor) and the inputs (RA CTWD and CTWDsetpoint) that is more complex.

In accordance with on embodiment, the correction factor is input tothree (3) LUT's (or functions/algorithms executed by a processor) 1120,1130, and 1140. Also, a preset travel speed is input to the first LUT1120, a preset weld duration is input to the second LUT 1130, and apreset workpoint is input to the third LUT 1140. In accordance with oneembodiment, the preset workpoint includes a wire feed speed (WFS) andwelding waveform parameters. The welding waveform parameters mayinclude, for example, one or more of a peak voltage, a peak current, apower, a pulse duration, a background amplitude, or a frequency. Thewelding waveform parameters are configured to operate at the WFS, inaccordance with one embodiment.

The output of the first LUT 1120 is an adjusted travel speed and theoutput of the second LUT 1130 is an adjusted weld duration. The outputof the third LUT 1140 is an adjusted WFS and an adjusted power sourceoutput. The adjusted power source output may include, for example, oneor more of a welding output voltage or a welding output current. Theadjusted parameters compensate for deviations in a deposit level(height) from a desired deposit level (desired height) for the currentweld layer at each of multiple positions as the current weld layer isbeing deposited. The relationship between the inputs and the outputs ofthe LUTs (or functions/algorithms executed by a processor) aredetermined experimentally or through analysis based on theory. Thecompensation is performed in real time at each location on the currentweld layer.

In this manner, fine corrections of deposition may be achieved in realtime for a current weld layer.

In accordance with another embodiment, a combination of the twoapproaches (i.e., making corrections in real time for the current weldlayer and making corrections for a next weld layer based on the currentweld layer) can be implemented. Such a combined approach may result in acombination of coarse correction and fine correction that helps to keepthe height of the layers more consistent with each other. For example,in one embodiment, the approach of correcting, in real time, on thecurrent weld layer may provide for fine corrections at many differentpositions on the current weld layer, and the approach of correcting onthe next weld layer may provide a single coarse correction for the nextweld layer. However, once the next weld layer becomes the current weldlayer, fine correction may again be applied.

For example, in one embodiment, a welding system is provided having awelding power source 72. The welding power source 72 is configured tosample, in real time, instantaneous parameter pairs during a roboticwelding additive manufacturing process while creating a current weldlayer of a 3D workpiece part. Each instantaneous parameter pair of theinstantaneous parameter pairs includes a welding output current and awire feed speed. The welding power source 72 is also configured todetermine an instantaneous contact tip-to-work distance in real timefor, and based on at least, each parameter pair of the instantaneousparameter pairs as each parameter pair is sampled during creation of thecurrent weld layer.

The welding power source 72 is further configured to determine, in realtime, a running average contact tip-to-work distance based on eachinstantaneous contact tip-to-work distance as each instantaneous contacttip-to-work distance is determined during creation of the current weldlayer. The welding power source 72 is also configured to determine atotal average contact tip-to-work distance based on each instantaneouscontact tip-to-work distance determined over the entire current weldlayer. The total average contact tip-to-work distance may be a simplemathematical average of the instantaneous contact tip-to-work distancesdetermined over the entire current weld layer or a weighted average ofthe instantaneous contact tip-to-work distances determined over theentire current weld layer.

The welding power source 72 is further configured to adjust, in realtime, a weld duration, a travel speed, or a wire feed speed of thewelding system during creation of the current weld layer in response tothe running average contact tip-to-work distance. The welding powersource is also configured to generate a correction factor to be usedwhen creating a next weld layer of the 3D workpiece part based on atleast the total average contact tip-to-work distance.

In accordance with one embodiment, the welding power source includes acontroller 130 configured to determine the instantaneous contacttip-to-work distance, determine the running average contact tip-to-workdistance, and determine the total average contact tip-to-work distance.The controller 130 is also configured to adjust one or more of the weldduration, the travel speed, or the wire feed speed during the creationof the current weld layer, and generate the correction factor to be usedwhen creating the next weld layer. In one embodiment, the instantaneouscontact tip-to-work distance is further based on one or more of awelding output voltage, a welding electrode type, a welding electrodediameter, or a shielding gas used.

In one embodiment, adjusting the travel speed in response to the runningaverage contact tip-to-work distance includes taking into account apreset travel speed. Adjusting the weld duration in response to therunning average contact tip-to-work distance includes taking intoaccount a preset weld duration. Adjusting the wire feed speed inresponse to the running average contact tip-to-work distance includestaking into account a preset wire feed speed.

In one embodiment, the welding system includes a robot 14 having a robotcontroller 76 configured to operatively communicate with the weldingpower source 72, a welding tool 60 operatively connected to the robot14, and a wire feeder 68 operatively connected to the welding tool 60and the welding power source 72. In one embodiment, the correctionfactor is further based on 3D model parameters corresponding to the 3Dworkpiece part and/or robot parameters provided by the robot controller76 for a next weld operation for the next weld layer. The 3D modelparameters and the robot parameters may include one or more of adesignated height (designated deposition level) of the next weld layeror a designated position of a welding tool for the next weld layer.

In this manner, combined fine and coarse compensation for depositionlevels can be accomplished for a current weld layer and a next weldlayer, respectively, of a 3D workpiece part being additivelymanufactured.

An alternative way that fine corrections of deposition may be achievedin real time for a current weld layer are discussed next with respect toFIG. 12. Similarly to FIG. 11, FIG. 12 illustrates another exemplaryembodiment of a portion 1200 of the controller 130 of the welding powersource 72 of FIG. 2 to compensate for deviations in a deposit level(height) from a desired deposit level (desired height) for a currentweld layer. As shown in FIG. 12, the portion 1200 of the controller 130is configured to generate an adjusted travel speed, an adjusted weldduration, an adjusted wire feed speed (WFS), and an adjusted powersource output for the current layer. In accordance with one embodiment,the controller 130 of the welding power source 72 communicates theadjusted travel speed to the robot controller 76 such that the robotcontroller 76 can drive the robot 14 to move the welding gun 60 at theadjusted travel speed. Similarly, the controller 130 of the weldingpower source 72 communicates the adjusted WFS to the wire feeder 68 suchthat the wire feeder 68 can drive the welding electrode (wire) at theadjusted WFS. However, in FIG. 12, the correction factor is a relativecorrection factor that is based on a ratio of wire feed speed andwelding output current, instead of CTWD.

Referring again to FIG. 12, a long term running average (LTRA) ratio(WFS/AMPS or AMPS/WFS) of the instantaneous WFS and the instantaneouswelding output current is being generated during deposition of a currentwelding layer. In accordance with one embodiment, the LTRA ratio isgenerated by the controller 130, for example, similar to how the RA CTWDis described herein as being generated. The LTRA ratio is generated overa period of time that is greater than or equal to a first defined periodof time. Similarly, a short term running average (STRA) ratio (WFS/AMPSor AMPS/WFS) of the instantaneous WFS and the instantaneous weldingoutput current is being generated during deposition of the currentwelding layer. In accordance with one embodiment, the STRA ratio isgenerated by the controller 130, for example, similar to how the RA CTWDis described herein as being generated. In one embodiment, the STRAratio is generated over a sliding window having a period of time that isshorter than the first defined period of time. For example, inaccordance with one embodiment, the STRA ratio may be initialized at thestart of a layer and then generated over a sliding window having a timeperiod of one (1) second. The LTRA ratio may be initialized at the startof a layer and then generated over a sliding window having a time periodof at least five (5) seconds, and may be reset to a LTRA setpoint valuewhen going to a next layer, for example. Other times and time periodsfor generating, initializing, and resetting the LTRA ratio and the STRAratio are possible as well, in accordance with other embodiments.

Referring again to FIG. 12, the STRA ratio is compared to the LTRA ratioby a comparator 1210. The output of the comparator 1210 is a relativecorrection factor. The relative correction factor may be a difference ofthe STRA ratio and the LTRA ratio, in accordance with one embodiment. Inaccordance with another embodiment, the comparator 1210 may be replacedby a LUT (or function/algorithm executed by a processor) providing arelationship between the output (relative correction factor) and theinputs (STRA ratio and LTRA ratio) that is more complex.

In accordance with on embodiment, the relative correction factor isinput to three (3) LUT's (or functions/algorithms executed by aprocessor) 1220, 1230, and 1240. Also, a preset travel speed is input tothe first LUT 1220, a preset weld duration is input to the second LUT1230, and a preset workpoint is input to the third LUT 1240. Inaccordance with one embodiment, the preset workpoint includes a wirefeed speed (WFS) and welding waveform parameters. The welding waveformparameters may include, for example, one or more of a peak voltage, apeak current, a power, a pulse duration, a background amplitude, or afrequency. The welding waveform parameters are configured to operate atthe WFS, in accordance with one embodiment.

The output of the first LUT 1220 is an adjusted travel speed and theoutput of the second LUT 1230 is an adjusted weld duration. The outputof the third LUT 1240 is an adjusted WFS and an adjusted power sourceoutput. The adjusted power source output may include, for example, oneor more of a welding output voltage or a welding output current. Theadjusted parameters compensate for deviations in a deposit level(height) from a desired deposit level (desired height) for the currentweld layer at each of multiple positions as the current weld layer isbeing deposited. The relationship between the inputs and the outputs ofthe LUTs (or functions/algorithms executed by a processor) aredetermined experimentally or through analysis based on theory. Thecompensation is performed in real time at each location on the currentweld layer.

In this alternate manner, fine corrections of deposition may be achievedin real time for a current weld layer.

In a similar manner to that previously described herein, combined fineand coarse compensation for deposition levels can be accomplished for acurrent weld layer and a next weld layer, respectively, of a 3Dworkpiece part being additively manufactured. The welding power source72 is also configured to determine a total average (TA) ratio (WFS/AMPSor AMPS/WFS) of the ratios of the instantaneous WFS and theinstantaneous welding output current for a current welding layer. Inaccordance with one embodiment, the TA ratio is generated by thecontroller 130 over the entire current weld layer, for example, similarto how the total average CTWD is described herein as being generated.The TA ratio may be a simple mathematical average of the ratios of theinstantaneous WFS and the instantaneous welding output currentdetermined over the entire current weld layer, or a weighted average ofthe ratios of the instantaneous WFS and the instantaneous welding outputcurrent determined over the entire current weld layer.

The welding power source 72 is further configured to adjust, in realtime, a weld duration, a travel speed, or a wire feed speed of thewelding system during creation of the current weld layer in response tothe relative correction factor which is based on the STRA ratio and theLTRA ratio. The welding power source is also configured to generate anext correction factor to be used when creating a next weld layer of the3D workpiece part based on at least the TA ratio.

In accordance with one embodiment, the welding power source includes acontroller 130 configured to determine the instantaneous ratios of WFSand welding output current, determine the STRA ratio and the LTRA ratio,and determine the TA ratio. The controller 130 is also configured toadjust one or more of the weld duration, the travel speed, or the wirefeed speed during the creation of the current weld layer based on therelative correction factor, and generate the next correction factor tobe used when creating the next weld layer.

In one embodiment, the welding system includes a robot 14 having a robotcontroller 76 configured to operatively communicate with the weldingpower source 72, a welding tool 60 operatively connected to the robot14, and a wire feeder 68 operatively connected to the welding tool 60and the welding power source 72. In one embodiment, the next correctionfactor is further based on 3D model parameters corresponding to the 3Dworkpiece part and/or robot parameters provided by the robot controller76 for a next weld operation for the next weld layer. The 3D modelparameters and the robot parameters may include one or more of adesignated height (designated deposition level) of the next weld layeror a designated position of a welding tool for the next weld layer.

In this manner, combined fine and coarse compensation for depositionlevels can be accomplished for a current weld layer and a next weldlayer, respectively, of a 3D workpiece part being additivelymanufactured.

In one embodiment, a welding system is provided having a welding powersource. The welding power source is configured to: sample, in real time,instantaneous parameter pairs of welding output current and wire feedspeed during a robotic welding additive manufacturing process forcreating a current weld layer of a 3D workpiece part; determine aninstantaneous contact tip-to-work distance for, and based on at least,each parameter pair of the instantaneous parameter pairs sampled duringcreation of the current weld layer; determine an average contacttip-to-work distance based on each instantaneous contact tip-to-workdistance determined for the current weld layer; and generate acorrection factor to be used when creating a next weld layer of the 3Dworkpiece part based on at least the average contact tip-to-workdistance. Each instantaneous contact tip-to-work distance may bedetermined in real time, and the welding power source may be furtherconfigured to: determine, in real time, a running average of contacttip-to-work distance as each instantaneous contact tip-to-work distanceis determined during creation of the current weld layer; and adjust, inreal time, one or more of a weld duration or a wire feed speed duringcreation of the current weld layer in response to the running average ofcontact tip-to-work distance. The instantaneous contact tip-to-workdistance may be further based on one or more of welding output voltage,welding electrode type, welding electrode diameter, and shielding gasused. The correction factor may affect one or more of weld duration,wire feed speed, or travel speed for the next weld layer. The correctionfactor may be further based on one or more of 3D model parameterscorresponding to the 3D workpiece part or robot parameters provided by arobot controller for a next weld operation for the next weld layer. The3D model parameters and robot parameters may include one or more of adesignated height of the next weld layer or a designated position of awelding tool for the next weld layer. The average contact tip-to-workdistance may be one of a simple mathematical average of theinstantaneous contact tip-to-work distances determined for the currentweld layer, a weighted average of the instantaneous contact tip-to-workdistances determined for the current weld layer, or a running average ofthe instantaneous contact tip-to-work distances determined for thecurrent weld layer. The welding system may include a robot having arobot controller configured to operatively communicate with the weldingpower source. The welding system may include a welding tool operativelyconnected to the robot. The welding system may include a wire feederoperatively connected to the welding tool and the welding power source.

In one embodiment, a welding system is provided having a welding powersource. The welding power source is configured to: sample, in real time,instantaneous parameter pairs of welding output current and wire feedspeed during a robotic welding additive manufacturing process forcreating a current weld layer of a 3D workpiece part; determine, in realtime, an instantaneous contact tip-to-work distance for, and based on atleast, each parameter pair of the instantaneous parameter pairs sampledduring creation of the current weld layer; determine, in real time, arunning average of contact tip-to-work distance as each instantaneouscontact tip-to-work distance is determined during creation of thecurrent weld layer; and adjust, in real time, one or more of a weldduration or a wire feed speed during creation of the current weld layerin response to the running average of contact tip-to-work distance. Thewelding power source may be further configured to: determine an averagecontact tip-to-work distance based on each instantaneous contacttip-to-work distance determined for the current weld layer; and generatea correction factor to be used when creating a next weld layer of the 3Dworkpiece part based on at least the average contact tip-to-workdistance. The instantaneous contact tip-to-work distance may be furtherbased on one or more of welding output voltage, welding electrode type,welding electrode diameter, and shielding gas used. The correctionfactor may affect one or more of weld duration, wire feed speed, ortravel speed for the next weld layer. The correction factor may befurther based on one or more of 3D model parameters corresponding to the3D workpiece part or robot parameters provided by a robot controller fora next weld operation for the next weld layer. The 3D model parametersand robot parameters may include one or more of a designated height ofthe next weld layer or a designated position of a welding tool for thenext weld layer. The welding system may include a robot having a robotcontroller configured to operatively communicate with the welding powersource. The welding system may further include a welding tooloperatively connected to the robot. The welding system may also includea wire feeder operatively connected to the welding tool and the weldingpower source.

In one embodiment, a welding system is provided having a welding powersource. The welding power source is configured to sample, in real time,instantaneous parameter pairs, where each instantaneous parameter pairof the instantaneous parameter pairs includes a welding output currentand a wire feed speed, during a robotic welding additive manufacturingprocess while creating a current weld layer of a 3D workpiece part. Thewelding power source is also configured to determine an instantaneousratio of welding output current and wire feed speed in real time foreach parameter pair of the instantaneous parameter pairs as eachparameter pair is sampled during creation of the current weld layer. Thewelding power source is further configured to determine, in real time, ashort term running average ratio of welding output current and wire feedspeed based on each instantaneous ratio of welding output current andwire feed speed as each instantaneous ratio of welding output currentand wire feed speed is determined during creation of the current weldlayer. The welding power source is also configured to generate arelative correction factor, based on at least the short term runningaverage ratio of welding output current and wire feed speed, to be usedin real time while creating the current weld layer of the 3D workpiecepart to compensate for deviations in a deposit level from a desireddeposit level for the current weld layer. In one embodiment, the weldingpower source is configured to generate, in real time, a long termrunning average ratio of welding output current and wire feed speedbased on each instantaneous ratio of welding output current and wirefeed speed as each instantaneous ratio of welding output current andwire feed speed is determined during creation of the current weld layer.The long term running average ratio is determined over a second periodof time that is longer than a first period of time over which the shortterm running average ratio is determined. In one embodiment, the shortterm running average ratio of welding output current and wire feed speedis one of a simple running mathematical average of the instantaneousratios of welding output current and wire feed speed or a weightedrunning average of the instantaneous ratios of welding output currentand wire feed speed. In one embodiment, the welding power source isfurther configured to generate the relative correction factor at leastin part by comparing the short term running average ratio of weldingoutput current and wire feed speed to the long term running averageratio of welding output current and wire feed speed, and adjust, in realtime, one or more of a travel speed, a weld duration, or a wire feedspeed of the welding system during creation of the current weld layer inresponse to the relative correction factor. In one embodiment, adjustingthe travel speed in response to the relative correction factor includestaking into account a preset travel speed, adjusting the weld durationin response to the relative correction factor includes taking intoaccount a preset weld duration, and adjusting the wire feed speed inresponse to the relative correction factor includes taking into accounta preset wire feed speed. In one embodiment, the relative correctionfactor is further based on one or more of 3D model parameterscorresponding to the 3D workpiece part or robot parameters provided by arobot controller for a current weld operation for the current weldlayer. The 3D model parameters and robot parameters include one or moreof a designated height of the current weld layer or a designatedposition of a welding tool for the current weld layer. In oneembodiment, the welding system includes a robot having a robotcontroller configured to operatively communicate with the welding powersource. The welding system also includes a welding tool operativelyconnected to the robot, and a wire feeder operatively connected to thewelding tool and the welding power source.

In one embodiment, a welding system is provided having a welding powersource. The welding power source is configured to sample, in real time,instantaneous parameter pairs, where each instantaneous parameter pairof the instantaneous parameter pairs includes a welding output currentand a wire feed speed, during a robotic welding additive manufacturingprocess while creating a current weld layer of a 3D workpiece part. Thewelding power source is also configured to determine an instantaneousratio of welding output current and wire feed speed in real time for,and based on at least, each parameter pair of the instantaneousparameter pairs as each parameter pair is sampled during creation of thecurrent weld layer. The welding power source is further configured todetermine, in real time, a short term running average ratio of weldingoutput current and wire feed speed based on each instantaneous ratio ofwelding output current and wire feed speed as each instantaneous ratioof welding output current and wire feed speed is determined duringcreation of the current weld layer. The welding power source is alsoconfigured to determine a total average ratio of welding output currentand wire feed speed based on each instantaneous ratio of welding outputcurrent and wire feed speed determined over the entire current weldlayer. The welding power source is further configured to adjust, in realtime, one or more of a weld duration, a travel speed, or a wire feedspeed of the welding system during creation of the current weld layerbased at least in part on the short term running average ratio ofwelding output current and wire feed speed. The welding power source isalso configured to generate a next correction factor to be used whencreating a next weld layer of the 3D workpiece part based on at leastthe total average ratio of welding output current and wire feed speed.In one embodiment, the welding power source includes a controller thatis configured to determine the instantaneous ratio of welding outputcurrent and wire feed speed, determine the short term running averageratio of welding output current and wire feed speed, determine the totalaverage ratio of welding output current and wire feed speed, adjust oneor more of the weld duration, the travel speed, or the wire feed speedduring the creation of the current weld layer, and generate the nextcorrection factor to be used when creating the next weld layer. In oneembodiment, the welding power source is configured to determine, in realtime, a long term running average ratio of welding output current andwire feed speed based on each instantaneous ratio of welding outputcurrent and wire feed speed as each instantaneous ratio of weldingoutput current and wire feed speed is determined during creation of thecurrent weld layer. The long term running average ratio is determinedover a second period of time that is longer than a first period of timeover which the short term running average ratio is determined. In oneembodiment, adjusting the travel speed based on at least the short termrunning average ratio includes taking into account a preset travelspeed, adjusting the weld duration based on at least the short termrunning average ratio includes taking into account a preset weldduration, and adjusting the wire feed speed based on at least the shortterm running average ratio includes taking into account a preset wirefeed speed. In one embodiment, the next correction factor is furtherbased on one or more of 3D model parameters corresponding to the 3Dworkpiece part or robot parameters provided by a robot controller for anext weld operation for the next weld layer. The 3D model parameters androbot parameters include one or more of a designated height of the nextweld layer or a designated position of a welding tool for the next weldlayer. In one embodiment, the total average ratio is one of a simplemathematical average of the instantaneous ratios of welding outputcurrent and wire feed speed determined over the entire current weldlayer, a weighted average of the instantaneous ratios of welding outputcurrent and wire feed speed determined over the entire current weldlayer, or a running average of the instantaneous ratios of weldingoutput current and wire feed speed determined over the entire currentweld layer. In one embodiment, the welding system includes a robothaving a robot controller configured to operatively communicate with thewelding power source, a welding tool operatively connected to the robot,and a wire feeder operatively connected to the welding tool and thewelding power source.

In summary, a system and method to correct for height error during arobotic welding additive manufacturing process are provided. One or bothof a welding output current and a wire feed speed are sampled during arobotic welding additive manufacturing process when creating a currentweld layer. A plurality of instantaneous contact tip-to-work distances(CTWD's) are determined based on at least one or both of the weldingoutput current and the wire feed speed. An average CTWD is determinedbased on the plurality of instantaneous CTWD's. A correction factor isgenerated, based on at least the average CTWD, which is used tocompensate for any error in height of the current weld layer and/or thenext weld layer.

In appended claims, the terms “including” and “having” are used as theplain language equivalents of the term “comprising”; the term “in which”is equivalent to “wherein.” Moreover, in appended claims, the terms“first,” “second,” “third,” “upper,” “lower,” “bottom,” “top,” etc. areused merely as labels, and are not intended to impose numerical orpositional requirements on their objects. Further, the limitations ofthe appended claims are not written in means-plus-function format andare not intended to be interpreted based on 35 U.S.C. § 112, sixthparagraph, unless and until such claim limitations expressly use thephrase “means for” followed by a statement of function void of furtherstructure. As used herein, an element or step recited in the singularand proceeded with the word “a” or “an” should be understood as notexcluding plural of said elements or steps, unless such exclusion isexplicitly stated. Furthermore, references to “one embodiment” of thepresent invention are not intended to be interpreted as excluding theexistence of additional embodiments that also incorporate the recitedfeatures. Moreover, unless explicitly stated to the contrary,embodiments “comprising,” “including,” or “having” an element or aplurality of elements having a particular property may includeadditional such elements not having that property. Moreover, certainembodiments may be shown as having like or similar elements, however,this is merely for illustration purposes, and such embodiments need notnecessarily have the same elements unless specified in the claims.

As used herein, the terms “may” and “may be” indicate a possibility ofan occurrence within a set of circumstances; a possession of a specifiedproperty, characteristic or function; and/or qualify another verb byexpressing one or more of an ability, capability, or possibilityassociated with the qualified verb. Accordingly, usage of “may” and “maybe” indicates that a modified term is apparently appropriate, capable,or suitable for an indicated capacity, function, or usage, while takinginto account that in some circumstances the modified term may sometimesnot be appropriate, capable, or suitable. For example, in somecircumstances an event or capacity can be expected, while in othercircumstances the event or capacity cannot occur—this distinction iscaptured by the terms “may” and “may be.”

This written description uses examples to disclose the invention,including the best mode, and also to enable one of ordinary skill in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to one of ordinary skill in the art. Such other examples areintended to be within the scope of the claims if they have structuralelements that do not differentiate from the literal language of theclaims, or if they include equivalent structural elements withinsubstantial differences from the literal language of the claims.

While the claimed subject matter of the present application has beendescribed with reference to certain embodiments, it will be understoodby those skilled in the art that various changes may be made andequivalents may be substituted without departing from the scope of theclaimed subject matter. In addition, many modifications may be made toadapt a particular situation or material to the teachings of the claimedsubject matter without departing from its scope. Therefore, it isintended that the claimed subject matter not be limited to theparticular embodiments disclosed, but that the claimed subject matterwill include all embodiments falling within the scope of the appendedclaims.

What is claimed is:
 1. A welding system, comprising a welding power source, wherein the welding power source is configured to: sample, in real time, instantaneous parameter pairs, where each instantaneous parameter pair of the instantaneous parameter pairs includes a welding output current and a wire feed speed, during a robotic welding additive manufacturing process while creating a current weld layer of a 3D workpiece part; determine an instantaneous ratio of welding output current and wire feed speed in real time for each parameter pair of the instantaneous parameter pairs as each parameter pair is sampled during creation of the current weld layer; determine, in real time, a short term running average ratio of welding output current and wire feed speed based on each instantaneous ratio of welding output current and wire feed speed as each instantaneous ratio of welding output current and wire feed speed is determined during creation of the current weld layer; and generate a relative correction factor, based on at least the short term running average ratio of welding output current and wire feed speed, to be used in real time while creating the current weld layer of the 3D workpiece part to compensate for deviations in a deposit level from a desired deposit level for the current weld layer.
 2. The welding system of claim 1, wherein the welding power source is configured to generate, in real time, a long term running average ratio of welding output current and wire feed speed based on each instantaneous ratio of welding output current and wire feed speed as each instantaneous ratio of welding output current and wire feed speed is determined during creation of the current weld layer, wherein the long term running average ratio is determined over a second period of time that is longer than a first period of time over which the short term running average ratio is determined.
 3. The welding system of claim 1, wherein the short term running average ratio of welding output current and wire feed speed is one of a simple running mathematical average of the instantaneous ratios of welding output current and wire feed speed or a weighted running average of the instantaneous ratios of welding output current and wire feed speed.
 4. The welding system of claim 2, wherein the welding power source is further configured to: generate the relative correction factor at least in part by comparing the short term running average ratio of welding output current and wire feed speed to the long term running average ratio of welding output current and wire feed speed; and adjust, in real time, one or more of a travel speed, a weld duration, or a wire feed speed of the welding system during creation of the current weld layer in response to the relative correction factor.
 5. The welding system of claim 4, wherein: adjusting the travel speed in response to the relative correction factor includes taking into account a preset travel speed; adjusting the weld duration in response to the relative correction factor includes taking into account a preset weld duration; and adjusting the wire feed speed in response to the relative correction factor includes taking into account a preset wire feed speed.
 6. The welding system of claim 1, wherein the relative correction factor is further based on one or more of 3D model parameters corresponding to the 3D workpiece part or robot parameters provided by a robot controller for a current weld operation for the current weld layer.
 7. The welding system of claim 6, wherein the 3D model parameters and robot parameters include one or more of a designated height of the current weld layer or a designated position of a welding tool for the current weld layer.
 8. The welding system of claim 1, further comprising a robot having a robot controller configured to operatively communicate with the welding power source.
 9. The welding system of claim 8, further comprising a welding tool operatively connected to the robot.
 10. The welding system of claim 9, further comprising a wire feeder operatively connected to the welding tool and the welding power source.
 11. A welding system, comprising a welding power source, wherein the welding power source is configured to: sample, in real time, instantaneous parameter pairs, where each instantaneous parameter pair of the instantaneous parameter pairs includes a welding output current and a wire feed speed, during a robotic welding additive manufacturing process while creating a current weld layer of a 3D workpiece part; determine an instantaneous ratio of welding output current and wire feed speed in real time for, and based on at least, each parameter pair of the instantaneous parameter pairs as each parameter pair is sampled during creation of the current weld layer; determine, in real time, a short term running average ratio of welding output current and wire feed speed based on each instantaneous ratio of welding output current and wire feed speed as each instantaneous ratio of welding output current and wire feed speed is determined during creation of the current weld layer; determine a total average ratio of welding output current and wire feed speed based on each instantaneous ratio of welding output current and wire feed speed determined over the entire current weld layer; adjust, in real time, one or more of a weld duration, a travel speed, or a wire feed speed of the welding system during creation of the current weld layer based at least in part on the short term running average ratio of welding output current and wire feed speed; and generate a next correction factor to be used when creating a next weld layer of the 3D workpiece part based on at least the total average ratio of welding output current and wire feed speed.
 12. The welding system of claim 11, wherein the welding power source includes a controller, and wherein the controller is configured to: determine the instantaneous ratio of welding output current and wire feed speed; determine the short term running average ratio of welding output current and wire feed speed; determine the total average ratio of welding output current and wire feed speed; adjust one or more of the weld duration, the travel speed, or the wire feed speed during the creation of the current weld layer; and generate the next correction factor to be used when creating the next weld layer.
 13. The welding system of claim 11, wherein the welding power source is configured to determine, in real time, a long term running average ratio of welding output current and wire feed speed based on each instantaneous ratio of welding output current and wire feed speed as each instantaneous ratio of welding output current and wire feed speed is determined during creation of the current weld layer, wherein the long term running average ratio is determined over a second period of time that is longer than a first period of time over which the short term running average ratio is determined.
 14. The welding system of claim 11, wherein: adjusting the travel speed based on at least the short term running average ratio includes taking into account a preset travel speed; adjusting the weld duration based on at least the short term running average ratio includes taking into account a preset weld duration; and adjusting the wire feed speed based on at least the short term running average ratio includes taking into account a preset wire feed speed.
 15. The welding system of claim 11, wherein the next correction factor is further based on one or more of 3D model parameters corresponding to the 3D workpiece part or robot parameters provided by a robot controller for a next weld operation for the next weld layer.
 16. The welding system of claim 15, wherein the 3D model parameters and robot parameters include one or more of a designated height of the next weld layer or a designated position of a welding tool for the next weld layer.
 17. The welding system of claim 11, wherein the total average ratio is one of a simple mathematical average of the instantaneous ratios of welding output current and wire feed speed determined over the entire current weld layer, a weighted average of the instantaneous ratios of welding output current and wire feed speed determined over the entire current weld layer, or a running average of the instantaneous ratios of welding output current and wire feed speed determined over the entire current weld layer.
 18. The welding system of claim 11, further comprising a robot having a robot controller configured to operatively communicate with the welding power source.
 19. The welding system of claim 18, further comprising a welding tool operatively connected to the robot.
 20. The welding system of claim 19, further comprising a wire feeder operatively connected to the welding tool and the welding power source. 